// Copyright Epic Games, Inc. All Rights Reserved.

#include <zencore/md5.h>
#include <zencore/string.h>
#include <zencore/testing.h>
#include <zencore/zencore.h>

#include <string.h>
#include <string_view>

/*
 **********************************************************************
 ** md5.h -- Header file for implementation of MD5                   **
 ** RSA Data Security, Inc. MD5 Message Digest Algorithm             **
 ** Created: 2/17/90 RLR                                             **
 ** Revised: 12/27/90 SRD,AJ,BSK,JT Reference C version              **
 ** Revised (for MD5): RLR 4/27/91                                   **
 **   -- G modified to have y&~z instead of y&z                      **
 **   -- FF, GG, HH modified to add in last register done            **
 **   -- Access pattern: round 2 works mod 5, round 3 works mod 3    **
 **   -- distinct additive constant for each step                    **
 **   -- round 4 added, working mod 7                                **
 **********************************************************************
 */

/*
 **********************************************************************
 ** Copyright (C) 1990, RSA Data Security, Inc. All rights reserved. **
 **                                                                  **
 ** License to copy and use this software is granted provided that   **
 ** it is identified as the "RSA Data Security, Inc. MD5 Message     **
 ** Digest Algorithm" in all material mentioning or referencing this **
 ** software or this function.                                       **
 **                                                                  **
 ** License is also granted to make and use derivative works         **
 ** provided that such works are identified as "derived from the RSA **
 ** Data Security, Inc. MD5 Message Digest Algorithm" in all         **
 ** material mentioning or referencing the derived work.             **
 **                                                                  **
 ** RSA Data Security, Inc. makes no representations concerning      **
 ** either the merchantability of this software or the suitability   **
 ** of this software for any particular purpose.  It is provided "as **
 ** is" without express or implied warranty of any kind.             **
 **                                                                  **
 ** These notices must be retained in any copies of any part of this **
 ** documentation and/or software.                                   **
 **********************************************************************
 */

/* Data structure for MD5 (Message Digest) computation */
struct MD5_CTX
{
	uint32_t	  i[2];		  /* number of _bits_ handled mod 2^64 */
	uint32_t	  buf[4];	  /* scratch buffer */
	unsigned char in[64];	  /* input buffer */
	unsigned char digest[16]; /* actual digest after MD5Final call */
};

void MD5Init();
void MD5Update();
void MD5Final();

/*
 **********************************************************************
 ** End of md5.h                                                     **
 ******************************* (cut) ********************************
 */

/*
 **********************************************************************
 ** md5.c                                                            **
 ** RSA Data Security, Inc. MD5 Message Digest Algorithm             **
 ** Created: 2/17/90 RLR                                             **
 ** Revised: 1/91 SRD,AJ,BSK,JT Reference C Version                  **
 **********************************************************************
 */

/*
 **********************************************************************
 ** Copyright (C) 1990, RSA Data Security, Inc. All rights reserved. **
 **                                                                  **
 ** License to copy and use this software is granted provided that   **
 ** it is identified as the "RSA Data Security, Inc. MD5 Message     **
 ** Digest Algorithm" in all material mentioning or referencing this **
 ** software or this function.                                       **
 **                                                                  **
 ** License is also granted to make and use derivative works         **
 ** provided that such works are identified as "derived from the RSA **
 ** Data Security, Inc. MD5 Message Digest Algorithm" in all         **
 ** material mentioning or referencing the derived work.             **
 **                                                                  **
 ** RSA Data Security, Inc. makes no representations concerning      **
 ** either the merchantability of this software or the suitability   **
 ** of this software for any particular purpose.  It is provided "as **
 ** is" without express or implied warranty of any kind.             **
 **                                                                  **
 ** These notices must be retained in any copies of any part of this **
 ** documentation and/or software.                                   **
 **********************************************************************
 */

/* -- include the following line if the md5.h header file is separate -- */
/* #include "md5.h" */

/* forward declaration */
static void Transform(uint32_t* buf, uint32_t* in);

static unsigned char PADDING[64] = {0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
									0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
									0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
									0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};

/* F, G and H are basic MD5 functions: selection, majority, parity */
#define F(x, y, z) (((x) & (y)) | ((~x) & (z)))
#define G(x, y, z) (((x) & (z)) | ((y) & (~z)))
#define H(x, y, z) ((x) ^ (y) ^ (z))
#define I(x, y, z) ((y) ^ ((x) | (~z)))

/* ROTATE_LEFT rotates x left n bits */
#define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32 - (n))))

/* FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4 */
/* Rotation is separate from addition to prevent recomputation */
#define FF(a, b, c, d, x, s, ac)                        \
	{                                                   \
		(a) += F((b), (c), (d)) + (x) + (uint32_t)(ac); \
		(a) = ROTATE_LEFT((a), (s));                    \
		(a) += (b);                                     \
	}
#define GG(a, b, c, d, x, s, ac)                        \
	{                                                   \
		(a) += G((b), (c), (d)) + (x) + (uint32_t)(ac); \
		(a) = ROTATE_LEFT((a), (s));                    \
		(a) += (b);                                     \
	}
#define HH(a, b, c, d, x, s, ac)                        \
	{                                                   \
		(a) += H((b), (c), (d)) + (x) + (uint32_t)(ac); \
		(a) = ROTATE_LEFT((a), (s));                    \
		(a) += (b);                                     \
	}
#define II(a, b, c, d, x, s, ac)                        \
	{                                                   \
		(a) += I((b), (c), (d)) + (x) + (uint32_t)(ac); \
		(a) = ROTATE_LEFT((a), (s));                    \
		(a) += (b);                                     \
	}

void
MD5Init(MD5_CTX* mdContext)
{
	mdContext->i[0] = mdContext->i[1] = (uint32_t)0;

	/* Load magic initialization constants.
	 */
	mdContext->buf[0] = (uint32_t)0x67452301;
	mdContext->buf[1] = (uint32_t)0xefcdab89;
	mdContext->buf[2] = (uint32_t)0x98badcfe;
	mdContext->buf[3] = (uint32_t)0x10325476;
}

void
MD5Update(MD5_CTX* mdContext, unsigned char* inBuf, unsigned int inLen)
{
	uint32_t	 in[16];
	int			 mdi;
	unsigned int i, ii;

	/* compute number of bytes mod 64 */
	mdi = (int)((mdContext->i[0] >> 3) & 0x3F);

	/* update number of bits */
	if ((mdContext->i[0] + ((uint32_t)inLen << 3)) < mdContext->i[0])
		mdContext->i[1]++;
	mdContext->i[0] += ((uint32_t)inLen << 3);
	mdContext->i[1] += ((uint32_t)inLen >> 29);

	while (inLen--)
	{
		/* add new character to buffer, increment mdi */
		mdContext->in[mdi++] = *inBuf++;

		/* transform if necessary */
		if (mdi == 0x40)
		{
			for (i = 0, ii = 0; i < 16; i++, ii += 4)
				in[i] = (((uint32_t)mdContext->in[ii + 3]) << 24) | (((uint32_t)mdContext->in[ii + 2]) << 16) |
						(((uint32_t)mdContext->in[ii + 1]) << 8) | ((uint32_t)mdContext->in[ii]);
			Transform(mdContext->buf, in);
			mdi = 0;
		}
	}
}

void
MD5Final(MD5_CTX* mdContext)
{
	uint32_t	 in[16];
	int			 mdi;
	unsigned int i, ii;
	unsigned int padLen;

	/* save number of bits */
	in[14] = mdContext->i[0];
	in[15] = mdContext->i[1];

	/* compute number of bytes mod 64 */
	mdi = (int)((mdContext->i[0] >> 3) & 0x3F);

	/* pad out to 56 mod 64 */
	padLen = (mdi < 56) ? (56 - mdi) : (120 - mdi);
	MD5Update(mdContext, PADDING, padLen);

	/* append length in bits and transform */
	for (i = 0, ii = 0; i < 14; i++, ii += 4)
		in[i] = (((uint32_t)mdContext->in[ii + 3]) << 24) | (((uint32_t)mdContext->in[ii + 2]) << 16) |
				(((uint32_t)mdContext->in[ii + 1]) << 8) | ((uint32_t)mdContext->in[ii]);
	Transform(mdContext->buf, in);

	/* store buffer in digest */
	for (i = 0, ii = 0; i < 4; i++, ii += 4)
	{
		mdContext->digest[ii]	  = (unsigned char)(mdContext->buf[i] & 0xFF);
		mdContext->digest[ii + 1] = (unsigned char)((mdContext->buf[i] >> 8) & 0xFF);
		mdContext->digest[ii + 2] = (unsigned char)((mdContext->buf[i] >> 16) & 0xFF);
		mdContext->digest[ii + 3] = (unsigned char)((mdContext->buf[i] >> 24) & 0xFF);
	}
}

/* Basic MD5 step. Transform buf based on in.
 */
static void
Transform(uint32_t* buf, uint32_t* in)
{
	uint32_t a = buf[0], b = buf[1], c = buf[2], d = buf[3];

	/* Round 1 */
#define S11 7
#define S12 12
#define S13 17
#define S14 22
	FF(a, b, c, d, in[0], S11, 3614090360);	 /* 1 */
	FF(d, a, b, c, in[1], S12, 3905402710);	 /* 2 */
	FF(c, d, a, b, in[2], S13, 606105819);	 /* 3 */
	FF(b, c, d, a, in[3], S14, 3250441966);	 /* 4 */
	FF(a, b, c, d, in[4], S11, 4118548399);	 /* 5 */
	FF(d, a, b, c, in[5], S12, 1200080426);	 /* 6 */
	FF(c, d, a, b, in[6], S13, 2821735955);	 /* 7 */
	FF(b, c, d, a, in[7], S14, 4249261313);	 /* 8 */
	FF(a, b, c, d, in[8], S11, 1770035416);	 /* 9 */
	FF(d, a, b, c, in[9], S12, 2336552879);	 /* 10 */
	FF(c, d, a, b, in[10], S13, 4294925233); /* 11 */
	FF(b, c, d, a, in[11], S14, 2304563134); /* 12 */
	FF(a, b, c, d, in[12], S11, 1804603682); /* 13 */
	FF(d, a, b, c, in[13], S12, 4254626195); /* 14 */
	FF(c, d, a, b, in[14], S13, 2792965006); /* 15 */
	FF(b, c, d, a, in[15], S14, 1236535329); /* 16 */

	/* Round 2 */
#define S21 5
#define S22 9
#define S23 14
#define S24 20
	GG(a, b, c, d, in[1], S21, 4129170786);	 /* 17 */
	GG(d, a, b, c, in[6], S22, 3225465664);	 /* 18 */
	GG(c, d, a, b, in[11], S23, 643717713);	 /* 19 */
	GG(b, c, d, a, in[0], S24, 3921069994);	 /* 20 */
	GG(a, b, c, d, in[5], S21, 3593408605);	 /* 21 */
	GG(d, a, b, c, in[10], S22, 38016083);	 /* 22 */
	GG(c, d, a, b, in[15], S23, 3634488961); /* 23 */
	GG(b, c, d, a, in[4], S24, 3889429448);	 /* 24 */
	GG(a, b, c, d, in[9], S21, 568446438);	 /* 25 */
	GG(d, a, b, c, in[14], S22, 3275163606); /* 26 */
	GG(c, d, a, b, in[3], S23, 4107603335);	 /* 27 */
	GG(b, c, d, a, in[8], S24, 1163531501);	 /* 28 */
	GG(a, b, c, d, in[13], S21, 2850285829); /* 29 */
	GG(d, a, b, c, in[2], S22, 4243563512);	 /* 30 */
	GG(c, d, a, b, in[7], S23, 1735328473);	 /* 31 */
	GG(b, c, d, a, in[12], S24, 2368359562); /* 32 */

	/* Round 3 */
#define S31 4
#define S32 11
#define S33 16
#define S34 23
	HH(a, b, c, d, in[5], S31, 4294588738);	 /* 33 */
	HH(d, a, b, c, in[8], S32, 2272392833);	 /* 34 */
	HH(c, d, a, b, in[11], S33, 1839030562); /* 35 */
	HH(b, c, d, a, in[14], S34, 4259657740); /* 36 */
	HH(a, b, c, d, in[1], S31, 2763975236);	 /* 37 */
	HH(d, a, b, c, in[4], S32, 1272893353);	 /* 38 */
	HH(c, d, a, b, in[7], S33, 4139469664);	 /* 39 */
	HH(b, c, d, a, in[10], S34, 3200236656); /* 40 */
	HH(a, b, c, d, in[13], S31, 681279174);	 /* 41 */
	HH(d, a, b, c, in[0], S32, 3936430074);	 /* 42 */
	HH(c, d, a, b, in[3], S33, 3572445317);	 /* 43 */
	HH(b, c, d, a, in[6], S34, 76029189);	 /* 44 */
	HH(a, b, c, d, in[9], S31, 3654602809);	 /* 45 */
	HH(d, a, b, c, in[12], S32, 3873151461); /* 46 */
	HH(c, d, a, b, in[15], S33, 530742520);	 /* 47 */
	HH(b, c, d, a, in[2], S34, 3299628645);	 /* 48 */

	/* Round 4 */
#define S41 6
#define S42 10
#define S43 15
#define S44 21
	II(a, b, c, d, in[0], S41, 4096336452);	 /* 49 */
	II(d, a, b, c, in[7], S42, 1126891415);	 /* 50 */
	II(c, d, a, b, in[14], S43, 2878612391); /* 51 */
	II(b, c, d, a, in[5], S44, 4237533241);	 /* 52 */
	II(a, b, c, d, in[12], S41, 1700485571); /* 53 */
	II(d, a, b, c, in[3], S42, 2399980690);	 /* 54 */
	II(c, d, a, b, in[10], S43, 4293915773); /* 55 */
	II(b, c, d, a, in[1], S44, 2240044497);	 /* 56 */
	II(a, b, c, d, in[8], S41, 1873313359);	 /* 57 */
	II(d, a, b, c, in[15], S42, 4264355552); /* 58 */
	II(c, d, a, b, in[6], S43, 2734768916);	 /* 59 */
	II(b, c, d, a, in[13], S44, 1309151649); /* 60 */
	II(a, b, c, d, in[4], S41, 4149444226);	 /* 61 */
	II(d, a, b, c, in[11], S42, 3174756917); /* 62 */
	II(c, d, a, b, in[2], S43, 718787259);	 /* 63 */
	II(b, c, d, a, in[9], S44, 3951481745);	 /* 64 */

	buf[0] += a;
	buf[1] += b;
	buf[2] += c;
	buf[3] += d;
}

/*
 **********************************************************************
 ** End of md5.c                                                     **
 ******************************* (cut) ********************************
 */

#undef FF
#undef GG
#undef HH
#undef II
#undef F
#undef G
#undef H
#undef I

namespace zen {

//////////////////////////////////////////////////////////////////////////

MD5 MD5::Zero;	// Initialized to all zeroes

//////////////////////////////////////////////////////////////////////////

MD5Stream::MD5Stream()
{
	Reset();
}

void
MD5Stream::Reset()
{
}

MD5Stream&
MD5Stream::Append(const void* Data, size_t ByteCount)
{
	ZEN_UNUSED(Data);
	ZEN_UNUSED(ByteCount);

	return *this;
}

MD5
MD5Stream::GetHash()
{
	MD5 md5{};

	return md5;
}

//////////////////////////////////////////////////////////////////////////

MD5
MD5::HashMemory(const void* data, size_t byteCount)
{
	return MD5Stream().Append(data, byteCount).GetHash();
}

MD5
MD5::FromHexString(const char* string)
{
	MD5 md5;

	ParseHexBytes(string, 40, md5.Hash);

	return md5;
}

const char*
MD5::ToHexString(char* outString /* 32 characters + NUL terminator */) const
{
	ToHexBytes(Hash, sizeof(MD5), outString);
	outString[2 * sizeof(MD5)] = '\0';

	return outString;
}

StringBuilderBase&
MD5::ToHexString(StringBuilderBase& outBuilder) const
{
	char str[41];
	ToHexString(str);

	outBuilder.AppendRange(str, &str[40]);

	return outBuilder;
}

//////////////////////////////////////////////////////////////////////////
//
// Testing related code follows...
//

#if ZEN_WITH_TESTS

void
md5_forcelink()
{
}

// doctest::String
// toString(const MD5& value)
// {
// 	char md5text[2 * sizeof(MD5) + 1];
// 	value.ToHexString(md5text);

// 	return md5text;
// }

TEST_CASE("MD5")
{
	using namespace std::literals;

	auto Input	= "jumblesmcgee"sv;
	auto Output = "28f2200a59c60b75947099d750c2cc50"sv;

	MD5Stream Stream;
	Stream.Append(Input.data(), Input.length());
	MD5 Result = Stream.GetHash();

	MD5::String_t Buffer;
	Result.ToHexString(Buffer);

	CHECK(Output.compare(Buffer));

	MD5 Reresult = MD5::FromHexString(Buffer);
	Reresult.ToHexString(Buffer);
	CHECK(Output.compare(Buffer));
}

#endif

}  // namespace zen
